CN100458536C - Liquid crystal display and driving device of the same - Google Patents

Abstract

A liquid crystal display comprising: first and second oppositely spaced apart, insulating substrates; a pixel electrode formed on the first substrate; a common electrode formed on at least one of the first and second substrates; and A liquid crystal layer is interposed between the first substrate and the second substrate. According to this structure, each pixel electrode is divided into a main pixel electrode and a sub-pixel electrode, and different signal voltages are respectively applied to the main pixel electrode and the sub-pixel electrode at the same gray scale. In addition, the signal voltage to be applied to the sub-pixel electrode is determined by a gamma value satisfying the following equation: gamma K=(current gray level/maximum gray level) ^f where f (gray level)=α ×(maximum gray level/current gray level), and α is a constant.

Description

Liquid crystal display and its driving device

This application claims priority from Korean Patent Application No. 10-2004-0089646 filed on November 5, 2004, the contents of which are incorporated herein by reference.

technical field

The present invention generally relates to a liquid crystal display "LCD" and a driving device thereof. More particularly, the present invention relates to an LCD with improved visibility and a driving device thereof.

Background technique

Generally, an LCD includes: a pair of panels each having electrodes on inner surfaces thereof; and a dielectric anisotropic liquid crystal layer interposed between the panels. In LCD, the change of the voltage difference between the field generating electrodes, that is, the change of the intensity of the electric field generated by the electrodes, changes the transmittance of light passing through the LCD, therefore, the desired image is obtained by controlling the voltage difference between the electrodes .

However, the viewing angle of the LCD is not as wide as it needs to be. Therefore, in the field of LCDs, various methods for overcoming such defects have been proposed. One of the most prominent of recently proposed methods for securing a wider viewing angle is a method of vertically aligning liquid crystal molecules with upper and lower panels and forming a hole pattern or a protrusion pattern in a field generating electrode.

Specifically, the aperture pattern forming method utilizes a fringe field occurring in the vicinity of apertures formed in the pixel electrode and the common electrode. That is, the fringe field controls the tilt direction of the liquid crystal molecules to ensure a wider viewing angle.

The protrusion forming method utilizes a protrusion portion formed on the pixel electrode and the common electrode of the upper panel. These protrusions distort the electric field generated between the two electrodes, thereby controlling the tilt direction of the liquid crystal molecules.

In another method, holes are formed in the pixel electrodes of the lower panel, and protrusions are formed on the common electrodes of the upper panel. The fringe fields generated by the holes and protrusions control the tilt direction of the liquid crystal molecules, thereby forming a multi-domain structure, thereby ensuring a wide viewing angle.

In a multi-domain LCD, a viewing angle based on a contrast ratio of 10:1, or a viewing angle based on grayscale conversion defined as a critical angle for brightness conversion between grayscales is greater than 80 degrees in all directions. Despite this better characteristic, this LCD exhibits poor visibility at the left and right sides of the screen due to the inconsistency between the gamma curves at the front and the gamma curves at the sides. For example, in a patterned vertical alignment (“PVA”) mode LCD, where an aperture pattern is formed in the common electrode to form a multi-domain structure, when the viewing point moves from the very center to the edge of the screen, the brightness of the shield becomes higher and the color becomes closer to white. In more extreme cases, the intervals between gray levels become too narrow, and images may appear blurry.

Recently, attention to the visibility of LCDs has increased due to the increased use of LCDs for enjoying moving images and still images in the multimedia field.

Contents of the invention

The present invention realizes an LCD with excellent visibility, such as by providing a pixel electrode divided into two sub-pixel electrodes and applying different voltages to the two sub-pixel electrodes, respectively.

In an exemplary embodiment of the present invention, there is provided an LCD, including: a first insulating substrate; a second insulating substrate opposite to the first insulating substrate and separated from the first insulating substrate; a plurality of pixel electrodes formed on the first substrate; a common electrode formed on at least one of the first substrate and the second substrate; and a liquid crystal layer interposed in the first substrate between the bottom and the second substrate.

According to this structure, each pixel electrode is divided into a main pixel electrode and a sub-pixel electrode to form a plurality of main pixel electrodes and sub-pixel electrodes, and the plurality of main pixel electrodes and sub-pixel electrodes are respectively applied at the same gray scale. different signal voltages.

In addition, the signal voltage to be applied to the sub-pixel electrode is determined using a gamma value satisfying the following equation:

Gamma K=(current gray level/maximum gray level) ^f

Among them, f (gray level)=α×(maximum gray level/current gray level),

and α is a constant.

Here, preferably, the gamma value of the main pixel electrode is obtained by subtracting the gamma value of the sub-pixel electrode from twice the target gamma value, and the main pixel electrode and the sub-pixel electrode are performed according to all rows sort, or sort by all columns.

The LCD may further include a thin film transistor ("TFT") formed on the first substrate to turn on or off a signal voltage applied to the pixel electrode.

The main pixel electrode and the sub-pixel electrode have regions different from each other, and both the pixel electrode and the common electrode may include domain forming means.

The LCD may further include: a plurality of gate lines formed on the first substrate; and a plurality of data lines insulated from and crossing the gate lines.

Preferably, the domain forming means includes two portions formed at 45 degrees with respect to the gate lines and perpendicular to each other. The portion may include linearly formed holes in the pixel electrode and the common electrode.

At the same gray scale, the signal voltage applied to the main pixel electrode is higher than the signal voltage applied to the sub-pixel electrode. A main pixel electrode and a group of sub-pixel electrodes together serve as a pixel unit and represent one color.

In another exemplary embodiment of the present invention, there is provided an apparatus for driving a display device, the apparatus outputs a gate control signal and a data control signal after receiving an input control signal from an external apparatus, the apparatus in An image signal for a sub-pixel and an image signal for a main pixel are output after receiving an input image signal from an external device.

Here, the image signal for the main pixel is determined using a gamma value satisfying the following equation:

Gamma K=(current gray level/maximum gray level) ^f

Among them, f (gray level)=α×(maximum gray level/current gray level),

and α is a constant.

This means comprises a look-up table LUT for storing image signals for main pixels and image signals for sub-pixels against all image signals used in the display device, said means detecting An image signal for sub-pixels and an image signal for main pixels opposite to the image signal are input, and the detected image signal is output.

In this device, preferably, the gamma value for determining the image signal for the main pixel is obtained by subtracting the gamma value for determining the image signal for the sub-pixel from twice the target gamma value.

In another exemplary embodiment of the present invention, an LCD is provided, including: a first insulating substrate; a gate line formed on the first insulating substrate and having a gate electrode; a gate insulating layer, formed on the gate line; an amorphous silicon layer formed on the gate insulating layer; an ohmic contact formed on the amorphous silicon layer; a data line formed on the gate insulating layer , which at least partially includes a source electrode formed on the ohmic contact; a drain electrode, opposite to the source electrode, at least partially on the ohmic contact; a passivation layer formed on the data line and the drain electrode; a pixel electrode formed on the passivation layer and connected to the drain electrode; a second insulating substrate opposite to the first insulating substrate; a common electrode formed On said second substrate; first domain forming means formed on at least one of said first substrate and said second substrate; second domain forming means formed on said first substrate and on at least one of said second substrates, together with said first domain forming means, divides the pixel area into a plurality of sub-domains.

According to this structure, the pixel electrode is divided into a main pixel electrode and a sub-pixel electrode, and different signal voltages are respectively applied to the main pixel electrode and the sub-pixel electrode at the same gray scale.

In addition, the signal voltage of the main pixel electrode is determined using a gamma value satisfying the following equation

Gamma K=(current gray level/maximum gray level) ^f

Among them, f (gray level)=α×(maximum gray level/current gray level),

and α is a constant.

In another exemplary embodiment of the present invention, an LCD is provided, including a plurality of pixel electrodes, the pixel electrodes are divided into main pixel electrodes and sub-pixel electrodes, and at the same gray level, respectively Different signal voltages are applied to the electrode and the sub-pixel electrode, and the signal voltage to be applied to the sub-pixel electrode is determined by using the gamma value Gamma K=(current gray level/maximum gray level) ^f , where the index f is not a constant.

The index f changes for the current gray level, and the minimum value of f occurs at the maximum gray level. The index f is determined using the equation f(gray level)=α×(maximum gray level/current gray level), where α is a constant.

The gamma value of the main pixel electrode is obtained by subtracting the gamma value of the sub-pixel electrode from twice the target gamma value.

The sub-pixel electrode has a different size from the main pixel electrode, and a signal voltage applied to the main pixel electrode is higher than a signal voltage applied to the sub-pixel electrode at the same gray scale.

Description of drawings

The above objects and other advantages of the present invention will become more apparent by describing preferred embodiments of the present invention with reference to the accompanying drawings, in which:

1 is a block diagram of an exemplary embodiment of an LCD according to the present invention;

FIG. 2 is an exploded perspective view schematically showing an exemplary embodiment of an LCD according to the present invention;

3 is an equivalent circuit diagram of a typical embodiment of a pixel unit of an LCD according to the present invention;

Fig. 4 has shown the typical embodiment according to the pixel arrangement of TFT panel of the present invention;

FIG. 5 is a layout diagram of a typical embodiment of a TFT panel according to the present invention;

6 is a layout diagram of an exemplary embodiment of a color filter plate according to the present invention;

7 is a layout diagram of an exemplary embodiment of an LCD according to the present invention;

Fig. 8 is a sectional view taken along line VIII-VIII' of Fig. 7;

9 is a graph showing typical gamma curves of main pixels and sub-pixels and their average gamma curves in an exemplary embodiment of an LCD according to the present invention; and

10 is a graph showing typical gamma curves of main pixels and sub-pixels and their average gamma curves in another exemplary embodiment of an LCD according to the present invention.

Detailed ways

Now, preferred embodiments of the present invention will be described in more detail hereinafter with reference to the accompanying drawings in which preferred embodiments of the invention are shown. However, the invention may be embodied in different forms and should not be construed as limited to only the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the invention to those skilled in the art.

In the drawings, the thickness of layers, films and regions are exaggerated for clarity. Hereinafter, the same numerals denote the same elements. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present.

Hereinafter, LCDs according to preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an exemplary embodiment of an LCD according to the present invention, FIG. 2 is an exploded perspective view schematically showing an exemplary embodiment of an LCD according to the present invention, and FIG. 3 is a pixel unit of an LCD according to the present invention. The equivalent circuit diagram of the embodiment.

Referring to FIG. 1 , the LCD includes an LC panel assembly 300, a gate driver 400 connected to the LC panel assembly 300, a data driver 500, a gray scale voltage generator 800 connected to the data driver 500, and a light source for supplying light to the LC panel assembly 300. The light source part 960, the light source driver 920 for controlling the light source part 960, and the signal controller 600 for controlling the above-mentioned elements.

Referring to FIG. 2, the LCD includes: an LC module 350 including a display unit 330 and a rear unit 340; a front case 361 and a rear case 362 (optionally referred to as a front frame and a rear frame, respectively) for accommodating and supporting LC module 350; and molding frames 363 and 364.

The display unit 330 includes an LC panel assembly 300, a gate tape carrier package ("TCP") 410 and a data TCP 510 attached to the LC panel assembly 300, and a gate printed circuit board ("TCP") attached to the respective TCPs 410 and 510, respectively. "PCB") 450 and data PCB 550. Alternatively, the gate and data TCPs 410 and 510 may be chip-on-film ("COF") type packages.

In the structure shown in FIGS. 2 and 3, the LC panel assembly 300 includes a lower panel 100 as a thin film transistor ("TFT") panel and an upper panel 200 as a color filter panel, wherein the panels 100 and 200 face each other, And the LC layer 3 is interposed therebetween. In the circuit shown in FIGS. 1 and 3, the LC panel assembly 300 also includes a plurality of display signal lines G ₁ -G _n and D ₁ -D _m , and a plurality of display signal lines connected thereto, substantially in a matrix form in the circuit diagram aligned pixels.

The display signal lines G ₁ -G _n and D ₁ -D _m are arranged on the lower panel 100, and include a plurality of gate lines G ₁ -G _n for transmitting gate signals (also called "scanning signals"), and A plurality of data lines D ₁ -D _m for transmitting data signals. The gate lines G ₁ -G _n substantially extend in the row direction and are substantially parallel to each other, while the data lines D ₁ -D _m substantially extend in the column direction and are substantially parallel to each other.

Each pixel includes a switching element Q connected to the display signal lines G ₁ -G _n and D ₁ -D _m , and an LC capacitor C _LC and a storage capacitor C _ST connected to the switching element Q. In alternative embodiments, the storage capacitor C _ST may be omitted.

A switching element Q such as a TFT is provided on the lower panel 100, and has three terminals including a control terminal connected to one of the gate lines _G1 - _Gn , an input terminal connected to one of the data lines _D1 - _Dm , and an output terminal connected to the LC capacitor C _LC and the storage capacitor C _ST .

The LC capacitor C _LC includes, as two terminals thereof, a pixel electrode 190 disposed on the lower panel 100 and a common electrode 270 disposed on the upper panel 200 . The LC layer 3 interposed between the two electrodes 190 and 270 serves as a dielectric of the LC capacitor _CLC . The pixel electrode 190 is connected to the switching element Q, and supplies the common voltage V _com to the common electrode 270, and the common electrode 270 covers the entire surface of the upper panel 200, or substantially the entire surface. In an alternative embodiment, the common electrode 270 may be disposed on the lower panel 100, and at least one of the pixel electrode 190 and the common electrode 270 may be formed in a stripe shape or a strip shape.

The storage capacitor C _ST is an auxiliary capacitor of the LC capacitor C _LC . When the pixel electrode 190 and a separate signal line (not shown) provided on the lower panel 100 overlap each other with an insulator interposed therebetween, the overlapped portion becomes the storage capacitor C _ST . A predetermined voltage, such as a common voltage V _com , is supplied to the separated signal lines. Alternatively, the storage capacitor C _ST may be formed by overlapping the pixel electrode 190 with an adjacent gate line (ie, a previous gate line directly in front of the pixel electrode 190 ) with an insulator interposed therebetween.

For a color display, each pixel uniquely displays one of three colors (i.e., spatially partitioned), such as one of the three primary colors or one of red, blue, and green, or displays the three in sequence according to time Color (ie, temporal division), such as one of the three primary colors or one of red, blue, and green, whereby the spatial or temporal sum of colors is identified as the desired color. While examples of color sets include red, green, and blue, it should be understood that alternative color sets may be employed. FIG. 3 shows an example of space division, wherein, in a region of the upper panel 200 corresponding to the pixel electrode 190, each pixel includes a color filter 230 for displaying one color. In an alternative embodiment, the color filter 230 may be disposed above or below the pixel electrode 190 of the lower panel 100 .

Referring again to FIG. 2 , the backlight unit 340 forming a part of the light source part 960 is installed under the LC panel assembly 300 . The backlight unit 340 includes: a light source unit 349 including a plurality of light-emitting diodes (LEDs) 344 arranged in phantom on a PCB 345; a light guide plate 342; and a plurality of light sheets arranged between the LC board assembly 300 and the LEDs 344 (optical sheet) 343 for diffusing or adjusting light emitted from the LED 344 to the LC panel assembly 300. The backlight unit 340 also includes a reflection plate 341, which is disposed on the PCB 345 and includes a plurality of holes, wherein the light-emitting chips of the LED 344 pass through and protrude, so that the light emitted from the LED 344 The light is reflected to the LC panel assembly 300 . The holes may be circular such that the respective LEDs 344 protrude through the holes. Alternative shapes for the light aperture, such as a rectangular or elongated shape suitable for protruding a predetermined number of LEDs 344, are also within the scope of these embodiments. A radiant heat component made of thermally conductive material may be attached to the PCB 345 to radiate heat. The backlight unit 340 also includes a molding frame 364 disposed between the reflection plate 341 and the light guide plate 342 for maintaining a regular interval between the light source unit 349 and the light guide plate 342 and relative to the light source unit 349. to support the light guide plate 342 and the light sheet 343 . A power supply voltage is applied to the light source unit 349 from a power supply.

The LEDs 344 as light sources may use only white LEDs emitting white light, or a mixed array of red, green and blue LEDs. Mixed arrays of white and red LEDs can also be used. In this case, the red LED acts as an auxiliary to the white LED. LEDs are arranged on the PCB 345 in a predetermined form, thereby forming the light source unit 349. Each PCB 345 can be arranged horizontally along the longitudinal axis and can be sequentially loaded with red, green and blue LEDs 344. The number of LEDs 344 can vary, and alternative arrangements of LEDs 344 are within the scope of these embodiments.

FIG. 2 shows three light source units 349, but the number of light source units 349 may vary according to required brightness and the size of the LCD.

Although LEDs 344 are shown located within light source unit 349, backlight unit 340 may alternatively use fluorescent lamps, such as cold cathode fluorescent lamps (“CCFL”), external electrode fluorescent lamps (“EEFL”), etc., as light sources.

One or more polarizers may be disposed on the outer surfaces of the two panels 100 and 200 for polarizing the light emitted from the light source unit 349 . Typical polarizers 12 and 22 are shown in FIG. 8 .

Referring to FIGS. 1 and 2, the gray voltage generator 800 generates voltages of a plurality of gray levels related to the brightness of the LCD. The gray voltage generator 800 may be included in the data PCB 550 , generate two sets of gray voltages related to the transmittance of pixels, and supply the gray voltages to the data driving part 500 . Under the control of the signal controller 600, the data driving part 500 supplies gray voltages selected for each of the data lines _D1 - _Dm to the data lines as data signals, respectively. The grayscale voltages in one group have positive polarity with respect to the common voltage _Vcom , and the grayscale voltages in the other group have negative polarity with respect to the common voltage _Vcom .

On each of the gate TCPs 410 are mounted gate drivers 400 respectively, the gate drivers 400 having the shape of an integrated circuit (“IC”) chip, and connected to the gate lines G ₁ -G _n of the LC panel assembly 300, respectively. , for transmitting a gate signal input from an external device and composed of a combination of a gate-on voltage V _on and a gate-off voltage V _off to the gate signal lines G ₁ -G _n .

Data drivers 500 are respectively mounted on each data TCP 510, the data drivers 500 have the shape of an IC chip, and are respectively connected to the data lines D1- _Dm of the LC panel assembly ₃₀₀ for converting the slave grayscale voltage generator The data voltage selected from the gray voltages provided by 800 is transmitted to the data signal lines D ₁ -D _m .

In another embodiment of the present invention, the gate driver 400 or the data driver 500 may be directly mounted on the lower panel 100 instead of the TCP, with IC chips as in a "chip on glass"("COG") type mounting. shape, and in another embodiment of the present invention, the gate driver 400 or data driver 500 is integrated together with other components such as switching elements Q, gate lines G ₁ -G _n and data lines D ₁ -D _m into The lower panel 100. In the above case, the gate PCB 450 or the gate TCP 410 may be omitted.

Just as the data PCB 550 may be installed with the gray voltage generator 800, the signal controller 600 may be included in the data PCB 550 or the gate PCB 450 for controlling the operation of the gate driver 400 or the data driver 500. The signal controller 600 may also transmit a signal to the light source part 960 .

Hereinafter, the operation of the above-mentioned LCD will be described in detail.

Signal controller 600 receives red, green, and blue input image signals R, G, and B from an external graphics controller (not shown), and input control signals for controlling their display, such as vertical synchronous signal Vsync, horizontal synchronous signal Hsync, master clock signal MCLK, data enable signal DE, etc. In response to the input image signals R, G, and B and the input control signal, the signal controller 600 appropriately processes the image signals R, G, and B for the operation of the LC panel assembly 300, and generates a gate control signal CONT1 and a data control signal CONT2, Then, the gate control signal CONT1 and the data control signal CONT2 are provided to the gate driver 400 and the data driver 500, respectively. The signal controller 600 may also provide a backlight control signal to the light source part 960 .

In addition, the signal controller 600 has a look-up table LUT. The signal controller 600 detects the image signal of the sub-pixel and the image signal of the main pixel from the look-up table LUT with respect to the input image signals R, G, and B, and then transmits the detected image signal to the data driver using the image signal DAT. 500.

The sub-pixel image signal stored in the look-up table LUT exhibits lower luminance than the input image signals R, G, and B, while the main-pixel image signal exhibits a higher height than the input image signals R, G, and B, as follows Described further.

The gate control signal CONT1 includes: a vertical synchronization start signal STV, that is, a scan start signal, which is used to notify the start of a frame and has an instruction to start scanning; at least one gate clock signal CPV, which is used to control the gate conduction voltage V an output time of _on ; and an output enable signal OE for defining the duration of the gate turn-on voltage V _on .

The data control signal CONT2 includes: a horizontal synchronization start signal STH for notifying the data driver 500 of the start of data transmission for a group of pixels; a load signal LOAD having an instruction to apply a data voltage to the data lines _D1 - _Dm ; a reverse signal RVS, or an inversion signal, for reversing the polarity of the data voltage with respect to the common voltage V _com ; and a data clock signal HCLK.

In response to the data control signal CONT2 from the signal controller 600, the data driver 500 successively receives the image data DAT and the processed image signal for one row of pixels from the signal controller 600, and performs shifting to convert the image data DAT into a grayscale voltage The generator 800 provides the analog data voltage selected from the gray voltages, and then supplies the data voltage to the data lines D ₁ -D _m .

In response to the gate control signal CONT1 from the signal controller 600, the gate driver 400 supplies the gate- _on voltage Von to the gate lines _G1 - _Gn , thereby turning on the switching elements Q connected thereto. The data voltages supplied to the data lines _D1 - _Dm are supplied to corresponding pixels through the activated switching elements Q.

The difference between the data voltage supplied to the pixel and the common voltage V _com is represented as the charging voltage across the LC capacitor C _LC , ie, the pixel voltage. The LC molecules in the LC capacitor C _LC have different orientations according to the magnitude of the pixel voltage.

The light source driver 920 controls the current applied to the light source portion 960 for switching the LEDs 344 of the light source portion 960, and also controls the brightness of the light from the LEDs 344.

When the light emitted from the LED 344 passes through the LC layer 3, the polarization of the light changes according to the orientation of the LC molecules. Polarizers such as polarizers 12 and 22 convert differences in the polarization of light into differences in light transmission.

By repeating this process for one unit of horizontal time period (which is expressed as “1H” and equal to one time period of the horizontal synchronization signal Hsync, the data enable signal DE, and the gate clock signal CPV), during one frame, The gate- _on voltage Von is sequentially supplied to all the gate lines _G1 - _Gn , thereby applying the data voltage to all the pixels. When the next frame starts after finishing one frame, the inversion control signal RVS and part of the data control signal CONT2 applied to the data driver 500 are controlled so that the polarity of the data voltage is reversed with respect to the polarity of the previous frame. (Call this "frame inversion"). It is also possible to control the inversion control signal RVS, thereby inverting the polarity of the data voltage flowing along the data line in one frame (for example, row inversion and dot inversion), or inverting the polarity of the data voltage in one group Sexual inversion (for example, column inversion and dot inversion).

Fig. 4 shows a typical embodiment of the pixel arrangement of the TFT panel according to the present invention.

Referring to FIG. 4, a lower panel 100 as a TFT panel of this embodiment is provided with a plurality of pixels arranged substantially in a matrix. These pixels are defined such that multiple gate lines G ₁ , G2 , G3 . . . intersect multiple data lines D ₁ , D2 , D3. Each pixel has: a TFT as the switching element Q; and a pixel electrode, such as the pixel electrode 190, connected to the TFT.

In this structure, a pixel is divided into a main pixel and a sub-pixel according to a difference between gray voltages applied to corresponding pixel electrodes 190 . When two types of pixels exhibit the same gray scale, the voltage applied to the pixel electrode 190 of the main pixel is higher than the voltage applied to the pixel electrode 190 of the sub-pixel.

In this case, a set of main pixels and sub-pixels together act as a pixel unit that represents a color, improving visibility at the edges of the screen. That is, to compensate for any distortion of the gamma curve (representing the relationship between grayscale and brightness) caused when the viewing point is at the edge of the LCD, the pixel unit is divided into two parts, where: one part represents a lower brightness than the target , while the other part represents a brightness higher than the target brightness, thereby actually identifying the average brightness of the two parts. In other words, according to the portion, adjacent pixels have transmittances different from each other, so that visibility is enhanced.

In FIG. 4, main pixels and sub-pixels are alternately arranged either in rows or columns, but the arrangement of pixels can be changed in various ways.

Since the main pixels and sub-pixels are divided only according to the gray-scale voltage applied thereto, the main pixels and sub-pixels are similar in structure, but in any case, their dimensions can be controlled. That is, the dimensions of the sub-pixels may be different from the dimensions of the main pixels.

Hereinafter, the basic structure of a pixel will be described in more detail.

Figure 5 is a layout diagram of a typical embodiment of a TFT panel according to the present invention, Figure 6 is a layout diagram of a typical embodiment of a color filter board according to the present invention, and Figure 7 is a layout diagram of a typical embodiment of an LCD according to the present invention , and FIG. 8 is a cross-sectional view taken along line VIII-VIII' of FIG. 7 .

The lower panel 100 of the TFT panel as an LCD panel assembly is configured, which will be further described below.

A pixel electrode 190 made of a transparent conductive material such as indium tin oxide ("ITO") or indium zinc oxide ("IZO") is formed on an insulating substrate 110 made of a transparent material such as but not limited to glass. Made of insulating material. The pixel electrode 190 is connected to the TFT. According to this structure, the TFT is connected to the gate line 121 for transmitting a scanning signal and the data line 171 for transmitting an image signal, and turns on or off the image applied to the pixel electrode 190 in response to the scanning signal supplied through the gate line 121. Signal. The pixel electrode 190 includes an aperture pattern including three apertures 191 , 192 and 193 . The hole pattern divides the liquid crystal layer 3 into a plurality of regions having a common electrode hole pattern, which will be further described below. The pixel electrode hole pattern may include cutouts intersecting the pixel electrode 190 in a substantially angled direction with respect to the direction of the gate line 121 and the data line 171 , as shown by the holes 191 and 193 . The pixel electrode hole pattern may further include a cutout intersecting the pixel electrode 190 in a direction substantially perpendicular to the data line 171 , as indicated by the hole 192 . The hole 192 may also include a V-shaped portion opened in a direction adjacent to the data line 171 . Although specific eyelet patterns have been shown, alternative pixel electrode eyelet patterns would also be within the scope of these embodiments.

The lower polarizer 12 is disposed on the bottom surface of the insulating substrate 110 , and the upper polarizer 22 is disposed on the upper surface of the insulating substrate 210 . In a reflective LCD, the pixel electrode 190 could be made of a different material than a transparent material, and the lower polarizer 12 would not be necessary.

Next, the upper panel 200 as a color filter plate is configured, which will be further described below.

As shown in FIG. 6, a black matrix 220 for preventing light leakage, R, G, and B color filters 230, and a common electrode 270 made of a transparent conductive material such as ITO or IZO are formed on an insulating substrate. On the bottom 210, the insulating substrate 210 is made of a transparent insulating material such as but not limited to glass. The common electrode 270 includes an aperture pattern including apertures 271 , 272 and 273 . The hole pattern may include cutouts intersecting the common electrode 270 in a substantially angled direction with respect to directions of the gate lines 121 and the data lines 171 . For example, the common electrode hole pattern may include cutouts as shown by the hole 272 having a V shape larger than the V shape of the pixel electrode hole 192 . The common electrode hole pattern may further include: a cutout shown as the hole 271 parallel to one side of the V-shaped pattern; and another cutout shown as the hole 273 parallel to the other side of the V-shaped pattern. While the pixel electrode and the common electrode are separated by the liquid crystal layer 3 in the layer direction, the hole pattern of the pixel electrode and the common electrode are also separated in the horizontal direction, as shown in the example in FIG. 7 . Although specific patterns have been shown, alternative common electrode eyelet patterns would also be within the scope of these embodiments. The black matrix 220 may be formed on overlapping portions of the holes 271 , 272 and 273 and the color filter 230 and around the pixel region to prevent light from leaking through the holes 271 , 272 and 273 .

Hereinafter, the TFT panel 100 will be further described.

A plurality of gate lines 121 and a plurality of storage electrode lines 131 extending substantially in a horizontal direction are formed on the insulating substrate 110 of the TFT panel 100 .

Each gate line 121 includes a plurality of gate electrodes 124 protruding downward from the gate line 121, and each gate line 121 includes an end portion 125 having a relatively large size to be connected to an external device.

Each storage electrode line 131 includes a plurality of sets of storage electrodes 133a, 133b, and 133c. In one set of storage electrodes, two storage electrodes 133a and 133b extend in a vertical direction substantially parallel to the data line 171, and are connected to the remaining storage electrodes extending in a horizontal direction substantially parallel to the gate line 121 and the storage electrode line 131. The electrodes 133c are connected. The storage electrode 133c may be located substantially in the middle between adjacent gate lines 121, however, alternative locations for the storage electrode 133c may also be within the scope of the embodiments. Each storage wire line 131 may include more than two horizontal lines.

The gate lines 121 and the storage electrode lines 131 may be made of aluminum-containing metals (such as aluminum and/or aluminum alloys), silver-containing metals (such as silver and/or silver alloys), chromium (Cr), titanium (Ti), tantalum (Ta ), molybdenum (Mo), etc. In this embodiment, the gate lines 121 and the storage electrode lines 131 have a single layer structure. However, the gate line 121 and the storage electrode line 131 may have a double-layer structure including two metal layers having different physical properties. In this case, one of the two layers can be made of low-resistivity metals such as aluminum-containing metals or silver-containing metals, while the other layer can be made of metals such as chromium, molybdenum, titanium, tantalum, etc. that have outstanding physical and chemical properties. Made of special metal material.

Preferably, all lateral sides of the gate lines 121 and the storage electrode lines 131 are inclined by 30° to 80° with respect to the surface of the insulating substrate 110 .

A gate insulating layer 140 made of silicon nitride (SiNx) (just an example) or the like is formed on the gate line 121 and the insulating substrate 110, and may also be formed on the storage electrode line 131 and the storage electrodes 133a, 133b and 133c on.

A plurality of data lines 171 , a plurality of drain electrodes 175 and a plurality of under-bridge metal pieces 172 are formed on the gate insulating layer 140 . Therefore, although the data lines 171 and the gate lines 121 vertically cross each other, the gate insulating layer 140 insulates them from each other. Each data line 171 substantially extends in a vertical direction perpendicular to the gate line 121 , and includes a plurality of branch-shaped source electrodes 173 , each of which extends corresponding to each gate electrode 124 . Each UBM 172 is located on each gate line 121 .

Similar to the gate line 121, the data line 171, the drain electrode 175, and the under-bridge metal member 172 are made of chromium, aluminum, etc., and may have a single-layer structure or a multi-layer structure.

A plurality of linear semiconductors 151 made of hydrogenated amorphous silicon or the like are formed under the data lines 171 as shown in FIG. 8 , and under the drain electrodes 175 . Each linear semiconductor 151 extends substantially in a vertical direction and includes a plurality of branches each extending correspondingly to a respective gate electrode 124 , source electrode 173 and drain electrode 175 . Each branch forms a TFT channel 154 as shown in FIG. 5 .

A plurality of ohmic contacts 161 made of silicide or N+ hydrogenated amorphous silicon highly doped with N-type impurities are formed between the semiconductor 151 and the data line 171, and between the drain electrode 175 and the semiconductor 151, so that reduce the contact resistance between them.

A passivation layer 180 made of an inorganic insulating material such as SiN ₂ or an organic insulating material such as resin is formed on the data line 171 , the drain electrode 175 and the under bridge metal 172 , and on the gate insulating layer 140 .

The passivation layer 180 has a plurality of contact holes 181 and 183 through which at least a portion of the drain electrode 175 and the end portion 179 of the data line 171 are respectively exposed. A plurality of contact holes 182, 184 and 185 are formed so as to penetrate the passivation layer 180 and the gate insulating layer 140 to expose the end portion 125 of the gate line 121 and portions of the storage electrode 133a and the storage electrode line 131, respectively.

A plurality of pixel electrodes 190 , a plurality of contact assistants 95 and 97 , and a plurality of memory bridges 91 are formed on the passivation layer 180 . The pixel electrode 190, the contact assistants 95 and 97, and the storage bridge 91 are made of a transparent conductive material such as ITO, IZO or an opaque conductive material with good reflectivity such as aluminum.

The pixel electrode 190 is connected to the drain electrode 175 through the contact hole 181 . As previously described, three holes 191 , 192 and 193 are included in each pixel electrode 190 . The apertures 191 and 193 among the three apertures are formed at 45 degrees with respect to the gate line 121 while being perpendicular to each other. The remaining hole 192 is formed by digging (ie, notching) from the right vertical side to the left vertical side of the pixel electrode 190 in the horizontal direction. The opening of the hole 192 formed at the right vertical side of the pixel electrode 190 forms a funnel shape.

Each pixel electrode 190 is substantially symmetrical with respect to a line parallel to the gate line 121 that divides a pixel defined by the gate line 121 and the data line 171 intersecting each other into two.

Each storage bridge 91 is formed on the passivation layer 180, crosses the gate line 121, and is interconnected with two storage electrode lines 131 in adjacent pixel regions. The storage bridge 91 is connected to the storage electrode 133 a and the storage electrode line 131 through the contact holes 184 and 185 penetrating the passivation layer 180 and the gate insulating layer 140 . In addition, the storage bridge 91 overlaps the under-bridge metal piece 172 . Accordingly, the storage bridge 91 may be electrically interconnected with the entire storage electrode line 131 of the lower insulating substrate 110 . Accordingly, when any defect is detected in the gate line 121 or the data line 171 , the defective gate line 121 or the data line 171 may be repaired using the storage electrode line 131 . In addition, the under-bridge metal member 172 complements the electrical connection between the gate line 121 and the memory bridge 91 when a laser beam is irradiated to repair such a defective line.

The contact assistants 95 and 97 are connected to the end portion 125 of the gate line 121 and the end portion 179 of the data line 171 through the contact holes 182 and 183, respectively.

As previously described with respect to FIG. 6 , the black matrix 220 is disposed on the upper insulating substrate 210 to prevent light leakage, and the RGB color filters 230 are formed on the black matrix 220 . A common electrode 270 made of a transparent conductive material such as ITO, IZO, etc. is formed on the color filter 230 and has a plurality of sets of holes 271, 272 and 273.

As further shown in FIGS. 6 and 7, a group of holes 271, 272, and 273 includes: an inclined portion parallel to the holes 191 and 193 of the pixel electrode 190 formed at 45 degrees with respect to the gate line 121; The sides of the pixel electrodes 190 are overlapped. The end sections include two vertical end sections and two horizontal end sections. The apertures 191 and 193 of the pixel electrode 190 formed at 45 degrees with respect to the gate line 121 are disposed between the apertures 271 and 272 of the common electrode 270 and between the apertures 272 and 273 of the common electrode 270 . Other hole patterns for the pixel electrode 190 and the common electrode 270 should be within the scope of these embodiments.

When the above TFT panel 100 and color filter panel 200 are assembled, vertically aligned liquid crystal molecules are interposed therebetween in the liquid crystal layer 3, completing the LCD panel assembly.

In such an LCD panel assembly, a group of holes 271, 272, and 273 of the common electrode 270 and a group of holes 191, 192, and 193 of the pixel electrode 190 divide the pixel electrode 190 into a plurality of sub-regions. In this embodiment, the actual Above are eight sub-areas. As shown in FIG. 7, each sub-region is substantially longer and, therefore, differs in length and width.

A specific liquid crystal layer interposed between a sub-region of the pixel electrode 190 and a corresponding sub-region of the common electrode 270 may be referred to as a 'sub-region'. This sub-region can also be divided into four domains according to the average orientation of the long axes of the liquid crystal molecules when an electric field is generated.

In this manner, the pixel area is divided into multiple domains, and the direction of liquid crystal molecules in each domain is controlled, so that the LCD can have a wider viewing angle.

At the same time, edge visibility can be improved by supplying different grayscale voltages to main pixels and sub-pixels. Two important factors that affect edge visibility are the area ratio between the main pixel and the subpixel, and the gamma curve of the subpixel.

The area ratio between main pixels and sub-pixels is a structurally controllable factor. In other words, the area ratio can basically be controlled based on the desired brightness and actual edge visibility of the LCD.

Therefore, the gamma curve of sub-pixels is the most important factor to improve edge visibility.

In general, typical vertical, nematic mode LCDs have poor edge visibility. This is because the brightness at the edges is higher than the brightness at the front. In the case where the viewer's eye response is more sensitive, the increase in luminance occurs more rapidly at mid-gray levels, deteriorating visibility. It should be understood that grayscale includes grayscale levels ranging from true white to true black. The levels of gray (or white or black) are derived from the luminance portion of the signal. Therefore, a mid-gray level should be determined to be approximately halfway between true white and true black.

Therefore, in order to effectively improve edge visibility, the gamma curve of the sub-pixel should be set so that the brightness of the sub-pixel is kept at a fairly low level until the middle gray level, for example, 120 out of 256 gray levels. That is, in this embodiment, the brightness of the sub-pixels will be almost zero (at the lower limit of the gray scale) until about 120 gray scale.

The gamma value of the main pixel is calculated as follows. First, set the target gamma at the front face to be equal to the average gamma between the main pixel and the subpixel. Therefore, the gamma curve representing a frontal object will lie between the gamma curves of the main pixel and the subpixel. Therefore, by subtracting the gamma value of the sub-pixel from twice the target gamma value, the gamma value of the main pixel is obtained. In an alternative embodiment, the gamma value of the sub-pixel may be obtained by subtracting the gamma value of the main pixel from twice the target gamma value.

Typically, the gamma value K is set to satisfy the following Equation 1:

(equation 1)

Gamma K=(current gray level/maximum gray level) ^K

In this embodiment, by controlling the value of K in Equation 1, the gamma value of the sub-pixel is obtained.

For example, to improve visibility, when the gamma curve at the front is the one where K=2.4, the subpixel's gamma curve is set to K=9, thereby keeping the brightness for gray levels below 120 at a comparable level. Low values are almost close to zero. In this case, however, a problem arises when the brightness of the main pixel exceeds the maximum possible brightness of the LCD in the range of higher gray levels above 200. Therefore, as shown in Figure 9, in the gray scale range above 200, the gamma curve of the main pixel stays and remains at the maximum gamma level 1. In addition, the simulation result curve includes a discontinuous point around the gray level of about 200, and outside the above discontinuous range of the gray level above 200, the curve becomes lower than the positive target gamma curve. The presence of these discontinuities in the gamma curve may cause unnatural grayscale representations. It should be understood that in case the target gamma curve at the front side includes different values for K, the gamma curve of the primary pixel can reach a maximum gamma level of 1 at different gray levels. Additionally, it should also be understood that while this example includes gray levels extending to 256, alternative maximum gray levels may be employed.

If the gamma curve of the sub-pixel is set to a curve of K ≤ 5.5, the above problem can be solved, but the visibility will deteriorate.

Therefore, in another embodiment of the present invention, the gamma curve is determined by Equation 2 below.

(equation 2)

Gamma K=(current grayscale/maximum grayscale) ^f

f(grayscale)=α×(maximum grayscale/current grayscale),

where α is a constant.

According to Equation 2, the index f has a minimum value α at the maximum gray level, and α×1=α when the current gray level is equal to the maximum gray level. In addition, the exponent f increases as the gray level becomes smaller. Therefore, the exponent f is not a constant. Thus, the luminance for gray levels below 120 remains at a low level, almost close to zero, but the luminance for gray levels above 120 forms a more slowly increasing curve than the gamma curve produced by Equation 1 .

FIG. 10 shows the gamma curve when α=4.3 in Equation 2. For comparison, in this figure, the gamma curves of the main pixel and the sub-pixel in FIG. 9 are respectively represented by dotted lines. Although α = 4.3 in this embodiment, it should be understood that alternative constants for Equation 2 may be chosen.

As shown in Figure 10, in the gamma curve of the sub-pixel (indicated by alternating short and long dashed lines), for gray levels below 120, the brightness remains at a low level, almost close to zero, but for gray levels above 120 Grayscale, brightness goes up. At the gamma curve of this sub-pixel, the rising slope is gentler than that shown in FIG. 9 . For example, for gray levels of 120 and 200 when α=4.3, the index value f in Equation 2 is calculated as follows.

f(120)=4.3×(256/120)=9.17

f(200)=4.3×(256/200)=5.5

The resulting values correspond to K=9.17 and K=5.5 in Equation 1. Therefore, the index value changes relative to the current grayscale. The minimum value of the index is equal to the constant used in Equation 2 to obtain the index value, and when the current gray level is equal to the maximum gray level, the constant is used as the index value. The index increases as the current gray level decreases. Therefore, gamma curves of the main pixel for all grays can exist within the maximum gamma level. As mentioned above, according to Equation 2, the sub-pixel gamma curve does not cause any visually perceptible discontinuities and improves edge visibility. As a result, the viewing angle of the LCD becomes wider.

The present invention should not be considered limited to the particular examples described above, but rather should be construed to cover all aspects of the invention as fairly set forth in the appended claims. Various modifications, equivalents, and many constructions applicable to the present invention will be apparent to those skilled in the art having regard to the present invention upon review of this specification. Merely as an example, the hole pattern formed in the common electrode and the pixel electrode may be changed. Other modifications will also be apparent to those of ordinary skill in the art. However, the use of the terms first, second, etc. does not imply any order or importance, but rather the terms first, second, etc. are used to distinguish between various elements. Furthermore, the use of the term one does not denote a quantitative limitation, but rather indicates that there is at least one of the referenced item.

Claims (18)

1. A liquid crystal display, comprising: a first insulating substrate; a second insulating substrate opposite to the first insulating substrate and separated from the first insulating substrate; a plurality of pixel electrodes formed on the first substrate; a common electrode formed on at least one of the first substrate and the second substrate; and a liquid crystal layer interposed between said first substrate and said second substrate, Wherein, each pixel electrode is divided into a main pixel electrode and a sub-pixel electrode to which different signal voltages are respectively applied at the same gray level, so as to form a plurality of main pixel electrodes and sub-pixel electrodes, and Wherein, the signal voltage to be applied to the sub-pixel electrode is determined by using the gamma value satisfying the following equation: Gamma K=(current gray level/maximum gray level) ^f Among them, f (gray level)=α×(maximum gray level/current gray level), and α is a constant. 2. The liquid crystal display according to claim 1, wherein the gamma value of the main pixel electrode is obtained by subtracting the gamma value of the sub-pixel electrode from twice the target gamma value. 3. The liquid crystal display according to claim 1, wherein the main pixel electrodes and the sub-pixel electrodes are alternately arranged in all rows and all columns. 4. The liquid crystal display according to claim 1, further comprising a thin film transistor formed on the first substrate for turning on or off a signal voltage applied to the pixel electrode. 5. The liquid crystal display of claim 1, wherein the main pixel electrode and the sub-pixel electrode have areas different from each other. 6. The liquid crystal display of claim 1, wherein the pixel electrode and the common electrode each comprise a domain forming device. 7. The liquid crystal display according to claim 6, further comprising: a plurality of gate lines formed on the first substrate; and a plurality of data lines insulated from and intersecting the gate lines, Wherein, the domain forming device includes two parts formed at an angle of 45 degrees relative to the gate line, and the two parts are perpendicular to each other. 8. The liquid crystal display according to claim 7, wherein each portion is a linear hole in the pixel electrode and the common electrode. 9. The liquid crystal display according to claim 1, wherein at the same gray level, the signal voltage applied to the main pixel electrode is higher than the signal voltage applied to the sub-pixel electrode. 10. The liquid crystal display according to claim 1, wherein one main pixel electrode and one sub-pixel electrode together serve as a pixel unit and represent one color. 11. An apparatus for driving a display device, the apparatus outputs a gate control signal and a data control signal after receiving an input control signal from an external device, and the apparatus outputs a control signal for an input image after receiving an input image signal from an external device image signals for sub-pixels and image signals for main pixels, Wherein, a gamma value satisfying the following equation is used to determine an image signal for a sub-pixel: Gamma K=(current gray level/maximum gray level) ^f Among them, f (gray level)=α×(maximum gray level/current gray level), and α is a constant. 12. The apparatus according to claim 11, further comprising a look-up table for storing image signals of main pixels and image signals of sub-pixels for all image signals used in the display device, The device detects an image signal of a sub-pixel and an image signal of a main pixel for an input image signal from a lookup table, and outputs the detected image signal. 13. The apparatus according to claim 11, wherein the gamma used to determine the image signal of the main pixel is obtained by subtracting the gamma value used to determine the image signal of the sub-pixel from twice the target gamma value value. 14. A liquid crystal display, comprising: a first insulating substrate; a gate line, formed on the first insulating substrate, having a gate electrode; a gate insulating layer formed on the gate line; an amorphous silicon layer formed on the gate insulating layer; an ohmic contact formed on the amorphous silicon layer; a data line formed on the gate insulating layer at least partially including a source electrode formed on the ohmic contact; a drain electrode, opposite the source electrode, at least partially on the ohmic contact; a passivation layer formed on the data line and the drain electrode; a pixel electrode formed on the passivation layer and connected to the drain electrode; a second insulating substrate opposite to the first insulating substrate; a common electrode formed on the second substrate; first domain forming means formed on at least one of the first substrate and the second substrate; second domain forming means formed on at least one of said first substrate and said second substrate cooperates with said first domain forming means to divide a pixel area into a plurality of sub-domains, Wherein, the pixel electrode is divided into a main pixel electrode and a sub-pixel electrode, and different signal voltages are respectively applied to the main pixel electrode and the sub-pixel electrode at the same gray level, and Among them, the signal voltage of the main pixel electrode is determined by using the gamma value satisfying the following equation Gamma K=(current gray level/maximum gray level) ^f Among them, f (gray level)=α×(maximum gray level/current gray level), and α is a constant. 15. A liquid crystal display, comprising: A plurality of pixel electrodes are divided into main pixel electrodes and sub-pixel electrodes, and different signal voltages are respectively applied to the main pixel electrodes and sub-pixel electrodes at the same gray level, and Use the following gamma values to determine the signal voltage to be applied to the subpixel electrodes: Gamma K=(current gray level/maximum gray level) ^f , Here, f is determined using the equation f (gray level)=α×(maximum gray level/current gray level), where α is a constant. 16. The liquid crystal display of claim 15, wherein the gamma value of the main pixel electrode is obtained by subtracting the gamma value of the sub-pixel electrode from twice the target gamma value. 17. The liquid crystal display of claim 15, wherein the sub-pixel electrode has a different size from the main pixel electrode. 18. The liquid crystal display according to claim 15, wherein at the same gray level, the signal voltage applied to the main pixel electrode is higher than the signal voltage applied to the sub-pixel electrode.

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